Control device for a hydraulic control motor

ABSTRACT

A control device for a hydraulic control motor includes at least one valve controlled actively by an actuating force and at least one passive valve which is operatively connected to the actively controlled valve and which is co-controlled via a line.

FIELD OF THE INVENTION

The invention relates to a control device.

BACKGROUND INFORMATION

U.S. Pat. No. 3,714,868 describes a control device that operates on theclosed-center principle.

It is an object of the present invention to provide a control deviceconfigured to operate on the open-center principle and whichsubstantially avoids leakages. The control device may be constructed ina simple manner, may operate reliably and may be produced without a highoutlay in manufacturing terms.

SUMMARY

The above and other beneficial objects of the present invention areachieved by providing a control device as described herein.

In accordance with the present invention, quantity-independentfunctioning may be ensured. The control device according to the presentinvention may be used for various applications and may easily be adaptedto changed requirements. It may be used, for example, for a hydrauliccontrol motor, e.g., when the activation of the latter functions on theopen-center principle.

Example embodiments of the present invention are described herein.However, the present invention is not restricted to the featurecombinations described herein but include further appropriatepossibilities for the combination of features.

The present invention may allow a modular construction of the, e.g.,electrohydraulic control device, so that a large number of parts may beused many times, which may provide considerable advantages with regardto the outlay in terms of manufacturing and assembly terms. By virtue ofthe simple construction, standard seals may be used, which do not placestringent requirements on the components in terms of tolerances andsurface quality. In addition, the use of special materials may bedispensed with, which may be advantageous with regard to heat treatmentand surface treatment. At the same time, high flexibility for variousapplications is preserved. Particularly reliable functioning may beensured in that no moveable parts are mounted one in the other. When thecontrol device according to the present invention is used for ahydraulic control motor, the latter may be activated on the open-centeror closed-center principle.

A control device according to the present invention for a hydrauliccontrol motor has at least one valve which is controlled actively by anactuating force and which has a first piston with stepped diameters,which is mounted axially moveably in a housing and is loaded by a springand which forms a first pressure space with an, e.g., disk-shapedelement having a throttle point. Furthermore, such a control device hasat least one passive valve which is operatively connected to theactively controlled valve and which has a second piston with steppeddiameters, which is mounted axially moveably in the housing and isloaded by a spring and which forms with the housing a second pressurespace. These two pressure spaces are operatively connected via a line,so that the actively controlled valve co-controls the passive valve. Theactively controlled valve has an adjustable throttle point which may beregulated actively by a throttle needle. The actuating force whichregulates the throttle point may be applied mechanically, electrically,electromagnetically, hydraulically, pneumatically, etc. The pistons havespecial sealing elements which, in addition to performing their sealingfunction, also have bearing properties. They may be produced fromresistant and low-wear materials, such as, for example, Teflon.Integrated in the piston of the actively controlled valve is at leastone bore which serves for the feed of pressure medium into a pressurespace which is connected to the passive valve by a line.

An exemplary embodiment of the present invention is described below, inprinciple, with reference to the FIGURE.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE illustrates a control device according to the presentinvention which controls a hydraulic control motor.

DETAILED DESCRIPTION

A pressure medium conveyed out of a tank 2 by a pump 1 flows through aninflow bore 3 into a housing 4 having a plurality of bores 5,6,7,8 whichare connected via lines 9,10. A piston 12 loaded by a spring 11 ismounted axially moveably in the bore 5. The piston 12 has a steppedoutside diameter. A sealing element 13 in the piston 12 separates thebore 5 into two pressure spaces 14, 15. The sealing element 13 alsoserves at the same time for the low-friction guidance of the piston 12.The spring 11 is supported on a disk-shaped element 16 connected firmlyto the housing 4. The disk-shaped element 16 has a throttle point 17which co-operates with a throttle needle 18 axially displaceable by anactuating force and thus allows a change in volume flow.

The pressure medium flowing through the throttle point 17 flows througha further pressure space 24 and via a line 23 back to the tank. If, forexample, the volume flow in the inflow bore 3 is to be reduced orinterrupted, the throttle needle 18 is pushed into the throttle point17. The pressure medium then has to flow through a bore 19 arranged inthe piston 12. Due to the smaller throughflow cross-section of thethrottle points 17, there is a pressure build-up in the pressure space14. Beyond a defined pressure in the pressure space 14, a forceequilibrium occurs between the pressure forces acting on end faces 20and 21. The spring 11 has the task of pushing the piston 12, in theneutral position, against the housing 4 so that, due to the throttlingof the volume flow of the pressure medium in an annular gap 22, apredetermined pressure difference may arise, which, when a throttleeffect occurs at the throttle point 17, brings about, on the end face 21of the piston 12, a pressure force which overcomes the friction of thesealing element 13. When the force equilibrium is reached, the piston 12moves in the direction of the inflow bore 3 due to the force of thespring 11. The annular gap 22 located between the housing 4 and the endface 20 is thereby narrowed. As a result, the pressure of the pressuremedium of the inflow bore 3 rises. The actuating force on the throttleneedle 18 corresponds in amount to the pressure of the pressure mediumin the pressure space 14, which, in turn, corresponds to the pressure ofthe pressure medium in the inflow bore 3. This gives rise toproportionality between the actuating force acting on the throttleneedle 18 and the pressure of the pressure medium which is establishedin the inflow bore 3. A further piston 27 pressure-loaded by a spring 26is located in the bore 6 in the housing 4. The spring 26 is supported ona disk-shaped element 28.

If the pressure medium is to be led to a pressure space 40 of ahydraulic control motor 41 via a line 39, then a throttle needle 29 mayclose a throttle point 30, with the result that an annular gap 31 isclosed. The pressure medium flows through a bore 32 into a pressurespace 33 and from there further on, via a line 34, into a pressure space35 which is formed by a piston 36, axially displaceable in the bore 7,and the housing 4. The piston 36 pressure-loaded by a spring 37 closesan annular gap 38. A piston 42 of the hydraulic control motor 41 isdisplaced and the pressure medium is led further on from a secondpressure space 43 via a line 44 to the line 10 in the housing 4. Thepressure medium may flow off to the tank 2 via an open annular gap 45which occurs between the housing 4 and a piston 46 axially displaceablein the bore 8 and loaded by a spring 47.

A pressure space 50, which is formed by the housing 4 and the piston 46pressure-loaded by a spring 47, is operatively connected to the pressurespace 14 via a line 25.

An actively controlled valve 48 thus at the same time also controls apassive valve 49. A bore 52 may be provided, in addition, in the piston46 of the passive valve 49, in order to return the pressure medium intothe pressure space 14.

REFERENCE SYMBOLS

1. Pump

2. Tank

3. Inflow bore

4. Housing

5. Bore

6. Bore

7. Bore

8. Bore

9. Line

10. Line

11. Spring

12. Piston

13. Sealing element

14. Pressure space

15. Pressure space

16. Disk-shaped element

17. Throttle point

18. Throttle needle

19. Bore

20. End face

21. End face

21. End face

22. Annular gap

23. Line

24. Pressure space

25. Line

26. Spring

27. Piston

28. Disk-shaped element

29. Throttle needle

30. Throttle point

31. Annular gap

32. Bore

33. Pressure space

34. Line

35. Pressure space

36. Piston

37. Spring

38. Annular gap

39. Line

40. Pressure space

41. Hydraulic control motor

42. Piston

43. Pressure space

44. Line

45. Annular gap

46. Piston

47. Spring

48. Valve

49. Valve

50. Pressure space

51. Sealing element

52. Bore

What is claimed is:
 1. A control device for a hydraulic control motor,comprising: a housing; an element having a throttle point; at least onefirst valve including a first piston having a stepped diameter, thefirst piston mounted axially movably and loaded by a first spring, thefirst valve controllable in accordance with an actuating force, thefirst piston and the element arranged relative to the housing to form afirst pressure space; and at least one a second valve including a secondpiston having a stepped diameter, the second piston mounted axiallymovably and loaded by second a spring, the second piston arrangedrelative to the housing to form a second pressure space hydraulicallyconnected to the first pressure space via a line so that the secondvalve is arranged to be co-controlled by the first valve; wherein thecontrol device is configured to operate in accordance with anopen-center principle; and wherein at least one of the first piston andthe second piston includes a bore configured to feed pressure medium toa respective pressure space, the bore arranged so that the bore isclosed when the at least one of the first piston and the second pistonis pressed against the housing to avoid leakage.
 2. The control deviceaccording to claim 1, further comprising a throttle needle, the firstvalve controllable via the throttle point in accordance with thethrottle needle.
 3. The control device according to claim 1, furthercomprising an arrangement configured to generate an actuating force atleast one of mechanically, electrically, electromagnetically,hydraulically and pneumatically.
 4. The control device according toclaim 1, wherein each of the first piston and the second piston includesa sealing element configured to seal and mount.
 5. The control deviceaccording to claim 1, further comprising a first line path and a secondline path, the first line path and the second line path arranged inparallel between an inflow for a hydraulic pressure medium and a tank;wherein, in a direction of flow of the pressure medium during operation,each of the first line path and the second line path includes arespective first valve followed by a respective second valve, eachsecond valve configured to be co-controlled by the first valve arrangedin an opposite one of the first line path and the second line path.